/**
 * Copyright (c) 2010, Daniel Bimschas and Dennis Pfisterer, Institute of Telematics, University of Luebeck
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted provided that the
 * following conditions are met:
 *
 * 	- Redistributions of source code must retain the above copyright notice, this list of conditions and the following
 * 	  disclaimer.
 * 	- Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the
 * 	  following disclaimer in the documentation and/or other materials provided with the distribution.
 * 	- Neither the name of the University of Luebeck nor the names of its contributors may be used to endorse or promote
 * 	  products derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package de.uniluebeck.itm.nettyprotocols.isense.otap;

import com.coalesenses.tools.iSenseAes;
import com.coalesenses.tools.iSenseAes128BitKey;
import de.uniluebeck.itm.nettyprotocols.isense.iseraerial.ISerAerialIncomingPacket;
import de.uniluebeck.itm.nettyprotocols.isense.otap.generatedmessages.MacroFabricSerializer;
import de.uniluebeck.itm.nettyprotocols.util.HandlerTools;
import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.MessageEvent;
import org.jboss.netty.channel.SimpleChannelHandler;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class ISenseOtapPacketDecoder extends SimpleChannelHandler {

	private final Logger log;

	private iSenseAes aes = null;

	public ISenseOtapPacketDecoder() {
		this(null);
	}

	public ISenseOtapPacketDecoder(String instanceName) {
		log = LoggerFactory.getLogger(instanceName != null ? instanceName : ISenseOtapPacketDecoder.class.getName());
		log.debug("New instance");
	}

	@Override
	public void writeRequested(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
		Object msg = e.getMessage();

		if (msg instanceof ISenseOtapPacketDecoderSetAESKeyRequest) {
			iSenseAes128BitKey key = ((ISenseOtapPacketDecoderSetAESKeyRequest) msg).getKey();
			if (key != null) {
				log.info("Decrypting payload of otap packets");
				this.aes = new iSenseAes(key);
			} else {
				log.info("Disabled otap payload encryption");
				this.aes = null;
			}
		} else {
			super.writeRequested(ctx, e);
		}

	}

	@Override
	public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
		Object msg = e.getMessage();
		if (!(msg instanceof ISerAerialIncomingPacket)) {
			super.messageReceived(ctx, e);
			return;
		}

		ISerAerialIncomingPacket serAerialMsg = (ISerAerialIncomingPacket) msg;

		if (!serAerialMsg.getPayload().readable()) {
			super.messageReceived(ctx, e);
			return;
		}

		ChannelBuffer payload = serAerialMsg.getPayload();

		// Check if this is an OTAP packet
		if (payload.getByte(0) != ISenseOtapPacketType.OTAP) {
			super.messageReceived(ctx, e);
			return;
		}

		// Convert the payload to byte[]
		byte[] byteArray = new byte[payload.readableBytes()];
		payload.getBytes(payload.readerIndex(), byteArray, 0, byteArray.length);

		// Check if we need to decrypt the payload
		if (aes != null) {
			log.trace(("Encrypted otap payload wit AES"));
			byteArray = aes.decode(byteArray);

			if (byteArray == null) {
				log.trace("Unable to decrypt otap message. Message dropped");
				return;
			}
		}

		// Try to deserialize, if not, null is returned.
		Object result = MacroFabricSerializer.deserialize(byteArray);

		// Not an OTAP packet, return the original object
		if (result == null) {
			super.messageReceived(ctx, e);
			return;
		}

		// Return the decoded OTAP object
		HandlerTools.sendUpstream(result, ctx);
	}
}
